The data format as used for transmitting data via US National Weather Service NOAA Weather Radio (NWR) is for example described in the publication “NATIONAL WEATHER SERVICE—NOAA WEATHER RADIO (NWR) TRANSMITTERS—NWR SPECIFIC AREA MESSAGE ENCODING—NWR SAME”, Update #4.43 of Jul. 13, 1999. Background, details and examples of the NWR SAME system and data transmitted according to this system are described therein and are not repeated here in detail except when regarded helpful to understand the invention. In other countries or regions similar systems are being installed or tested, for which similar solutions as described herein may apply. For example in Germany the DCF77 time signal transmission is currently under development to also include a data string for weather or other warning functions.
According to NOAA SAME a typical string format is:
“ZCZC-WXR-EEE-PSSCCC-PSSCCC+TTTT-JJJHHMM-LLLLLLLL-”
Therein ZCZC is a header code block, a dash “-” is present between two code blocks, except prior to a message valid time, WXR identifies the organization transmitting the message (sometimes WXR is also referred to by ORG), EEE identifies the type of event, PSSCCC is the location data, TTTT is the duration data which identifies the time duration after the issue time for which the message is valid, JJJHHMM identifies calendar date and time, and LLLLLLLL identifies the originator of the message. There may be a single or several location data blocks, in the example two such blocks are shown.
This string is repeated three times with a pause after each string, and followed by further information. The latter may differ in length. Due to varying transmission conditions data may be corrupted at any location of the transmitted strings. In order to prevent a corrupted string to cause an erroneous warning or other action, code error checking is to be performed by the receiving device. The document regarding NOAA SAME mentioned above recommends performing a routine check as to whether at least two of the three strings are identical before a valid transmission is assumed. If this test fails, a bit-by-bit check of the three consecutively received strings is recommended, whereby only these bits are accepted as valid which appear identical in two of the three strings.
It is an object of the invention to improve the error checking process.